Rational design of phosphonate/quaternary amine block polymer as an high-efficiency antibacterial coating for metallic substrates

Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates.Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments(repeat units of 15)but varied cationic segments(repeat units of 8,45,and 70)were precisely prepared.Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate.Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations.Results showed that the antibacterial rate of the modified TC4 surface were 95.8%of S.aureus and 92.9%of E.coli cells attached.Interestingly,unlike the cationic free polymer or cationic hydrogels,the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity.In addition,the phosphonate/quate rnary amine block polymers can be easily constructed on titanium,stainless steel,and Ni/Cr alloy with significantly improved antibacterial property,indicating the generality of the block polymer for surface antibacterial modification of bio-metals.

Relation of Deposition Condition with Microstructure of YBCO Film and YSZ Buffer Layer on Metallic Substrate

icrostructures of two Yba_2Cu_3O_(7-y) (YBCO) film deposited on metal substrate (HastelloyC) with yttriastabilized zirconia (YSZ) buffer layer were studied comparatively. Relation of microstructure with deposition condition was also been discussed. The YSZ buffer layer with a low depositing rate is dense, even, textured and wellbonded to the substrate. On the contrary, the YSZ layer deposited with a high rate is loose and bonded badly to the substrate. Property and surface grain size of YBCO film are related to the substrate temperature (Ts) in the deposition process.

Microstructure of YBCO Superconducting Film on Metal Substrate with YSZ Buffer Layer

Microstructures of YBa_2Cu_3O_(7-y)(YBCO) film on flexible metal substrate with yttriastabilized zirconia(YSZ) buffer layer prepared by magnetron sputtering technique have been studied in this paper using transmission electron microscopy(TEM). A critical temperature(Tc) and a critical current density(Jc) of the YBCO film are 91 K and 2×103 A/cm2 at 77 K, 0 T respectively. Bonded steadfastly to the substrate of nickel alloy(HastelloyC), the dense, even and textured YSZ layer with fine crystal grains is about 12 μm thick. With an uneven thickness of about 500 nm, the YBCO layer is sometimes weakbonded to the YSZ layer. Impurities which occasionally led to cracks were observed at the YSZ/YBCO interface.

Tuning the alignment of pentacene on copper substrate by annealing-assistant surface functionalization

Controlling the alignment and packing structure of organic molecules on solid substrate surfaces at molecule level is essential to develop high-performance organic thin film(OTF)devices.Pentacene,which is a typical p-type semiconductor material usually adopts lying-down geometry on metal substrates owning toπ-d coupling between pentacene and metal substrates.However,in this study,we found that pentacene molecules can be adsorbed on an anneal-treated Cu(111)surface with their long axis perpendicular to substrate surface.Highly ordered single-layer pentacene film with stand-up molecular geometry was achieved on this substrate.It was found that the functionalization of Cu surface with C=O groups due to annealing treatment should be accounted for standing-up geometry of pentacene on Cu substrate.This observation shed light on the tuning of the alignment and packing structure of organic molecules.

Improved Semipolar(11(2|-)2) GaN Quality Grown on m-Plane Sapphire Substrates by Metal Organic Chemical Vapor Deposition Using Self-Organized SiN_x Interlayer

The effect of a self-organized SiNs interlayer on the defect density of （1122） semipolar GaN grown on 7n-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-ray diffrac- tion. The SiNx interlayer reduces the c-type dislocation density from 2.5 ×10^10 cm^-2 to 5 ×10^8 cm 2. The SiNx interlayer produces regions that are free from basal plane stacking faults （BSFs） and dislocations. The overall BSF density is reduced from 2.1×10^5 cm-1 to 1.3×10^4 cm^-1. The large dislocations and BSF reduction in semipolar （1122） GaN with the SiNx, interlayer result from two primary mechanisms. The first mechanism is the direct dislocation blocking by the SiNx interlayer, and the second mechanism is associated with the unique structure character of （1122） semipolar GaN.

Fabrication of InAlGaN/GaN High Electron Mobility Transistors on Sapphire Substrates by Pulsed Metal Organic Chemical Vapor Deposition

Nearly lattice-matched InAIGaN/GaN heterostructure is grown on sapphire substrates by pulsed metal organic chemical vapor deposition and excellent high electron mobility transistors are fabricated on this heterostructure. The electron mobility is 1668.08cm2/V.s together with a high two-dimensional-electron-gas density of 1.43 × 10^13 cm-2 for the InAlCaN/CaN heterostructure of 2Onto InAlCaN quaternary barrier. High electron mobility transistors with gate dimensions of 1 × 50 μm2 and 4μm source-drain distance exhibit the maximum drain current of 763.91 mA/mm, the maximum extrinsic transconductance of 163.13 mS/mm, and current gain and maximum oscillation cutoff frequencies of 11 GHz and 21 GHz, respectively.

Uncovering the magnetic response of open-shell graphene nanostructures on metallic surfaces at different doping levels

Open-shell graphene nanostructures(GNs)are promising candidates for future spintronics and quantum technologies.Recent progress based on on-surface synthetic approach has successfully created such GNs on metallic surfaces.Meanwhile,the doping effect of metallic surfaces is inevitably present and can significantly tune their electronic and magnetic properties.Here,we investigate the zigzag end states of open-shell 7-armchair graphene nanoribbons(7-AGNRs)on Au(111),Au(100)and Ag(111)surfaces.Combined with the manipulation of a scanning tunneling microscope,we demonstrate that the end states can be tuned from empty states to singly occupied states and to doubly occupied states by substrate doping.Furthermore,the singly occupied states can be finely tuned,with the occupancy number of the states and related magnetic behaviors uncovered by experiments at different temperatures and magnetic fields.Our results provide a comprehensive study of the magnetic response of open-shell GNs on metallic surfaces at different doping levels.

Substrate screening for superclean graphene growth using firstprinciples calculations

Suppressing the formation of amorphous surface carbon and contaminants during the preparation of graphene by chemical vapor deposition remains an ongoing issue.Herein,we analyzed how substrate characteristics affect graphene quality by simulating margin extension,the nucleation process,and defect pegging configurations on mono-crystalline oriented metal substrates with the aim of enhancing graphene cleanliness.Defect formation energy and nucleation potential,which are indirect substrate–graphene interaction features,were found to appropriately evaluate graphene quality.The crystallographic orientation of the metal substrate was discovered to be critical for producing superclean graphene.A low graphene defect density and high nucleation rate on the Cu(100)facet guarantee growth of high-quality graphene,especially in terms of suppressing the formation of amorphous carbon.In addition,rapid kink growth and self-healing on the Cu(100)facet facilitate rapid graphene synthesis,which is also promoted by rapid kink splicing and margin self-repair on this facet.This study provides theoretical insight useful for the synthesis of superclean graphene.

Research on Ce-Zr compounds on modifying γ-alumina washcoat on FeCrAl foils

Ce-Zr compounds such as Cc0.68Zr0.3202 solid solution, Ce/Zr nitrate and CeO2/ZrO2 were added into γ-alumina-based slurries, which were then loaded on FeCrAl foils pretreated at 950℃ and 1100℃. The microstructures and adhesion performance between the substrates and the washcoats were measured by SEM, BET surface area, ultrasonic vibration and thermal shock test. The results show that the addition of Ce0.68Zr0.32O2 solid solution, Ce/Zr nitrate and CeO2/ZrO2 into the slurries can improve γ-Al2O3-based washcoat adhesion on FeCrAl foils. Furthermore, ceria-zirconia solid solution increases the adhesion of the washcoat on the surface of an FeCrAl foil than the two others. The specific surface area of this washcoat remains about 4345 m^2/g and the weight loss is below 4.0% even after aging test of 10% steam-containing air at 1050℃ for 20 h.

Influence of Different Subsistence States of CeO_2^-ZrO_2 Mixed Oxides in Catalyst Coating on Catalytic Properties

The metallic substrate-catalysts with different subsistence states of CeO2-ZrO2 mixed oxides were prepared and the catalytic properties were investigated. The studies on CeO2-ZrO2-V2O5-CuO mixed oxides which were prepared by coprecipitation, show that the doping of V^5＋ and Cu^2＋ in CeO2-ZrO2 mixed oxides can enhance the catalytic activity and thermal stability of coating materials. Moreover, different additives were doped in slurries of γ-Al2O3 to investigate the influence of additives on oxidation activity of catalysts. The mixture of ceria-zirconia, alkali metals and other rare earths acting as additives exhibits promotion effect on oxidation activity by optimizing the distribution of oxygen on the surface and in the bulk of ceria species. This mentioned mixture was mixed with γ-Al2O3 and a newly proposed active component to prepare a new catalyst. Afterward, the influence of thermal treatment on the new catalyst were investigated by calcinations at 500, 650, 750, 800, 850 and 900 ℃ for 2 h. The light-off curves of CO and HC show that after being treated at 650 - 750 ℃, catalysts present the best activity. XRD patterns show that ceria and zirconia species in the newly proposed active component form a phase of extra CeO2-ZrO2 mixed oxides on the surface of catalysts after the thermal treatment at 750 ℃, which has practical value for improving the preparation process and promoting the catalytic properties. Moreover, XPS resuits imply the existence of Ce1-xPdxO2-σ and Ce1- xPtxO2-σ on the surface of these treated samples, which may show influence on the catalytic activities.

New Application of Stainless Steel

Several rigid substrates such as stainless steel, titanium alloy, aluminum alloy, nickel foil, silicon, and sodium lime glass have been employed for manufacturing high quality TiO2 films by metal organic chemical vapor deposition （MOCVD）. The as-deposited TiO2 films have been characterized with SEM/EDX and XRD. The photocatalytic properties were investigated by decomposition of aqueous orange Ⅱ. UV VIS photospectrometer was employed to check the absorption characteristics and photocatalytic degradation activity. The results show that films synthesized on metal substrates display higher photoactivities than that on absolute substrates such as silicon and glass. It is found that solar light is an alternative to UV-light used for illumination during photodegradation of orange Ⅱ. TiO2 film on stainless steel substrate was regarded as the best one for photocatalysis.

Theoretical study on magnetocaloric effect and its electric-field regulation in CrI_(3)/metal heterostructure

The extraordinary properties of a heterostructure by stacking atom-thick van der Waals(vdW)magnets have been extensively studied.However,the magnetocaloric effect(MCE)of heterostructures that are based on monolayer magnets remains to be explored.Herein,we deliberate MCE of vd W heterostructure composed of a monolayer CrI_(3)and metal atomic layers(Ag,Hf,Au,and Pb).It is revealed that heterostructure engineering by introducing metal substrate can improve MCE of CrI_(3),particularly boosting relative cooling power to 471.72μJ m^(-2)and adiabatic temperature change to 2.1 K at 5 T for CrI_(3)/Hf.This improved MCE is ascribed to the enhancement of magnetic moment and intralayer exchange coupling in CrI_(3)due to the CrI_(3)/metal heterointerface induced charge transfer.Electric field is further found to tune MCE of CrI_(3)in heterostructures and could shift the peak temperature by around 10 K in CrI_(3)/Hf,thus manipulating the working temperature window of MCE.These theoretical results could enrich the research on low-dimensional magnetocaloric materials.

Low threading dislocation density in GaN films grown on patterned sapphire substrates

The growth process of three-dimensional growth mode（3D） switching to two-dimensional growth mode （2D） is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical vapor deposition.The growth condition of the 3D-2D growth process is optimized to reduce the threading dislocation density（TDD）.It is found that the condition of the 3D layer is critical.The 3D layer keeps growing under the conditions of lowⅤ/Ⅲratio,low temperature,and high pressure until its thickness is comparable to the height of the cone-shaped patterns.Then the 3D layer surrounds the cone-shaped patterns and has inclined side facets and a top（0001） plane.In the following 2D-growth process,inclined side facets coalesce quickly and the interaction of TDs with the side facets causes the TDs to bend over.As a result,the TDD of GaN films can decrease to 1×10~8 cm^（-2）,giving full-width at half maximum values of 211 and 219 arcsec for（002） and（102） omega scans, respectively.

An implantable antibacterial drug-carrier:Mesoporous silica coatings with size-tunable vertical mesochannels

Implant-associated bacterial infection remains one of the most common and serious complications.Therefore,a surface boasting long-term antibacterial ability for implants is highly desirable.Herein,mesoporous silica coatings(MSCs)with vertical and size-tunable mesochannels are fabricated on a variety of metal substrates via a nano-interfacial oriented assembly approach.Such facile and versatile approach relies on the vertically oriented fusion of composite micelles on the nanoscale flatness surface of substrates.Such orientation assembly process endows the MSCs with vertical mesochannels,tunable mesopore size(ca.5.5-13.5 nm),and switchable substrates even with complex and diversified surfaces.Importantly,the MSCs on titanium substrates(Ti@MSCs)exhibit excellent performances for drug adsorption and sustained release.The saturation adsorption capacity can reach 0.544 μg·cm^(-2) towards minocycline hydrochloride(MC-HCl)antibiotic molecules,which is 6.5 times as the bare titanium(Ti)substrate.In addition,the drug release time can be controlled from 84 to 216 h by simply adjusting the mesopore size.As a proof of concept,the Ti@MSCs can realize a higher antibacterial rate(95.9%),compared with the bare Ti(70.3%).The results highlight the high potential of MSCs as implant coating for long-term preventing and eliminating peri-implantitis.

Bestow metal foams with nanostructured surfaces via a convenient electrochemical method for improved device performance

Metal foams have been intensively studied as three-dimensional （3-D） bulk mass-support for various applications because of their high conductivities and attractive mechanical properties. However, the relatively low surface area of conventional metal foams largely limits their performance in applications such as charge storage. Here, we present a convenient electrochemical method for addressing this problem using Cu foams as an example. High surface area Cu foams are fabricated in a one-pot one-step manner by repetitive electrodeposition and dealloying treatments. The obtained Cu foams exhibit greatly improved performance for different applications like surface enhanced Raman spectroscopy （SERS） substrates and 3-D bulk supercapacitor electrodes.

Self-assembled formation of long, thin, and uncoalesced GaN nanowires on crystalline TiN films

We investigate in detail the self-assembled nucleation and growth of vertically oriented GaN nanowires by molecular beam epitaxy on crystalline TiN films. We demonstrate that this type of substrate allows for the growth of long and thin GaN nanowires that do not suffer from coalescence, a problem common to the growth on Si and other substrates. Only beyond a certain nanowire length that depends on the nanowire density and exceeds here 1.5 bun, coalescence takes place by bundling, i.e. the same process as on Si. By analyzing the nearest neighbor distance distribution, we identify the diffusion-induced repulsion of neighboring nanowires as the main mechanism limiting nanowire density during nucleation on TiN. Since on Si the final density is determined by shadowing of the impinging molecular beams by existing nanowires, it is the difference in adatom surface diffusion that enables the formation of nanowire ensembles with reduced density on TiN. These nanowire ensembles combine properties that make them a promising basis for the growth of core-shell heterostructures.